Ukraine's volatile HIV epidemic, the worst in Europe, is concentrated in people who inject drugs (PWIDs). The most cost-effective primary and secondary HIV prevention and treatment strategy for Ukraine is to expand methadone maintenance treatment (MMT), especially for people living with HIV (PLH), but coverage remains low (2.7%) for the 310,000 PWIDs. MMT scale-up is hampered by complex, multi-level patient, provider, clinic and community factors. To reform healthcare, Ukraine has prioritized strengthening primary care. Our pilot study, based on the Collaborative Care Model, affirmed that integrating MMT into primary care for PLH was acceptable, feasible, convenient, reduced stigma and managed medical comorbidities (HIV, TB, HCV, depression, etc.) that was not otherwise handled in MMT specialty clinics. Three proposed evidence-based practices will reinforce Collaborative Care Model elements. Project ECHO uses a collaborative learning environment to continuously train, coach, and reinforce specialty care practices (e.g., managing comorbidities) for non-specialist physicians using tele-education technology. Quality Improvement (QI) techniques change clinical and organizational processes to achieve desired outcomes, provide analytical tools, and ensure stakeholder engagement. Pay-for-performance (P4P) incentives encourage physicians to achieve a core set of outcomes based on quality health indicators (QHIs), which are based on pre-specified process measures that yield the best P4P results. Study aims: 1) To compare both primary (composite QHI score) and secondary (individual QHI scores, quality of life, and stigma) outcomes in 1,350 HIV+ PWIDs receiving MMT from 15 regions (clusters) and 45 clinical settings using a stratified, phase-in, randomized cluster-controlled design over 24 months. After stratifying PWIDs based on current receipt of MMT, they will be randomized to receive MMT in specialty addiction clinics (N=450) or in an ECHO-IC/QI-enhanced primary care clinic with (N=450) or without (N=450) P4P incentives; 2) Using a multi-level implementation science framework, we will examine the contribution of client, clinician, and organizational factors that contribute to attaining optimal comprehensive QHI scores in the 1,350 recruited PWIDs in aim 1; and 3) To conduct modeling and cost-effectiveness analyses (CEA) of integrating MMT for people living with HIV into primary care, with or without P4P, compared to a control group of PWIDs receiving MMT in addiction specialty settings. Significance is based on Ukraine's high burden of HIV and other comorbidities in PWIDs, its regional leadership role in healthcare reform, and its priority to strengthen primary care. Innovation is reflected in strengthening of primary care through MMT integration using a nationwide RCT cluster design linked to an implementation science framework that provides empiric data to inform the CEA, its creative use of ECHO, QI techniques, and P4P, and its focus on processes and outcomes (multi-comorbidity QHIs) of integrated care. Feasibility is based on pilot testing, and extensive co-investigator experience with integrated care, RCTs, implementation science, stigma, ECHO, QI, P4P, and CEA, combined with numerous committed national and international stakeholders and a longstanding experience of conducting research on addiction, HIV, and TB in Ukraine.